Cancer, and a cure for it, are at the forefront of medical research throughout the world. However, the efficacy of treating cancer has changed little in the last four decades. Some of the daunting issues with regard to cancer are that there are many different types and each has its own characteristics. Moreover, many of these different types of cancer are being diagnosed more frequently as the population ages.
The cost of treating cancer on a case-by-case basis is staggering. Much of this cost is reflected by the high technology approaches being used now to treat cancer, such as bone marrow transplantation. It has been found, however, that the overall treatment cost for cancer can be drastically reduced if the cancer is detected early, or at a pre-cancerous state, when it is more susceptible to treatment.
When cancer is identified at the earliest stages, for example prior to its invasion of tissue, it is generally treatable. To illustrate, the advantage of finding tumors while they are small is that they can be completely removed surgically. However, as the primary tumor grows in size, there are local extensions away from it and the ability of the surgeon to remove all the tumor and diseased tissue decreases drastically. Therefore, the smaller the tumor, the more likely the success in treating it.
In determining how to treat a particular cancer, it is also important to stage (or grade) it, at the microscopic level, in tissue removed at the time of surgery. The purpose of examining the resected tissues in this way is to determine, at the microscopic level, the extent of the local spread of the cancer, whether the margin between the resected cancerous mass and the presumably healthy tissue that is left behind is free of cancer, and/or whether there is spread of cancer cells to regional lymph nodes. The microscopic level examination of tissues removed in surgery is an index of whether or not cancer cells have spread beyond the primary cancerous mass and the cancer is likely to grow again, either locally or at distant sites.
The microscopic examination of cancerous tissue and the tissue surrounding it that is believed normal tissue, hopefully will provide information as to whether there is local extension of the primary cancerous mass. This examination also provides a road map to determine which tissue in the patient may still be affected. The microscopic examination of lymph node tissue in the area around the cancerous mass, that typically is resected with the cancerous mass, is a factor in determining the success of the surgery and the therapy to subsequently treat the patient.
For example, in colon cancer, which is the second most common cancer in the United States and the developed world, the prognosis for success is directly related to the extent to which cancer cells penetrate the luminal surface of the colon into (or through) the colon wall. For a given depth of cancer cell penetration into the colon wall, the prognosis degrades as the number of regional lymph nodes with cancer cells increases. The relationships between the local extent of cancer and post-surgery prognosis apply to most cancers, e.g., breast, prostate, head, and neck cancer. As such, the staging of cancer by microscopic level examination of tissues removed during surgery is an important part of the medical treatment of cancer patients.
Presently, the staging of cancer is performed by microscopic level examination of the removed tissue. This method does not provide sufficient accuracy to predict the likelihood that cancer has spread beyond the immediate site of the primary tumor. Thus, it does not provide assurance that all the cancer cells have been removed from the patient. Obviously, there needs to be a practical way to obtain such information.
There is only a general relationship between prognosis and the extent of the local extension of cancers; however, this relationship is not absolute. Frequently, local and/or distant (metastatic) recurrences of cancers occur in patients whose tissue sections have margins that appear free of cancer cells as do the regional lymph nodes. The inability to properly stage cancer based on examination of the removed tissue results in the cancer cure rates being quoted in terms of long-term survival, e.g., 5 or even 10 years of disease free time after surgery.
Pathologists who examine the removed tissue have no adequate means to determine whether all the cancer was in fact removed from the patient. Moreover, they do not have a method to accurately stage the tissue that they have. In attempts to derive the needed accuracy for the staging process, pathologists have developed morphologic criteria to hopefully enhance the accuracy of predicting the biologic behavior of cancers. This process was intended to distinguish between small, apparently contained cancers that will not recur and those cancers that will recur. The prediction of recurrence of the cancer is based of the morphology of the cancer cells and how they are organized. This method for predicting the outcome also has not been successful.
The classification of cancer cells on the basis of their content of DNA and other biochemical measurements of cancer cells have not augmented significantly the predictive value of examining resected cancer tissues. As such, one of the conundrums of oncology and pathology is the well-known phenomena that some cancers behave aggressively to kill the patient while others that appear very similar, which may be found in the same organ, behave in a relatively benign way, i.e., they do not recur after the primary cancerous mass is removed.
Once surgery is completed to remove a cancerous mass, it normally is believed that no more cancerous tissue or cells remain. However, there is a high probability that all the cancer cells have not been removed; therefore, all post-surgical patients may be treated as if they still have cancer cells in their body. This is the case even when a pathology report of the resected tissue suggests that this is not so. The result of this is that a number of patients are treated unnecessarily with toxic drugs because physicians do not know how to identify the exact patients who have cancer cells remaining and who do not.
The poor predictive power of pathological examination of resected tissue may be founded on the fact that there are features of the growth and spread of cancer that are not understood. Moreover, it also may be founded on the fact that the current methods of pathology, which entail the subjective, microscopic examination of stained sections of tissues removed from patients, have proven to be incapable of identifying with any significant degree of accuracy whether or not cancer cells are present in tissues.
Cancer is a disease that evolves in a staged process. This is shown in FIG. 1. In FIG. 1, normal cell 100 will evolve to cancer cell 110 after going through dysplastic stage at 104 and neoplastic stage at 108. The cells at 104 refer to cells that have minimal changes due to pre-cancer. The neoplastic grade at 108 refers to cells that have moderate stages of pre-cancer. Such diagnoses alert the clinician that pre-cancer exists and that some type of treatment of the pre-cancer is needed to cure the condition and prevent the ultimate evolution of frank cancer. As would be understood, the identification of the developmental precursors to cancer cells would present the early detection of cancer. Treatment of cancer at this stage would prevent the evolution of these cells to frank cancer. Unfortunately, current technologies for detecting early stages of pre-cancer are neither sensitive nor specific.
As indicated, microscopic examination of tissues can fail to detect cancer cells. Moreover, current techniques of microscopic level examination of cells and tissues also can fail to detect cells that are intermediate stages of the evolution of normal cells to frank cancer.
The medical community has known for a long time the type of information that is needed to make more accurate and earlier diagnoses of cancer in examining tissue and cells. However, what has not been dealt with is how to obtain this information in an efficient and cost effective manner.
Research has established that the presence or absence of disease in cells and tissues is based on whether molecules are normal in-structure and whether a normal distribution of molecules is present in a given type of cell. This has led physicians to recognize that accurate diagnoses of disease may be based on a gathering and an evaluation of information at the molecular level in cells. As such, it has now become essential to perform molecular level analysis to diagnose diseases, like cancer, at early stages for the accurate detection of specific types of disease through the examination of cells and tissues.
There are two approaches to obtaining molecular level information regarding the presence or absence of disease in cells. The first uses molecular probes that search chemically for specific abnormal molecules. The second is to test for normal and abnormal molecules by measuring their interactions with electromagnetic radiation. The latter method is referred to as spectroscopy.
Spectroscopy has some advantages over the use of chemical or molecular probes in that spectroscopy can make measurements without prior knowledge of the exact type of abnormality present. Further, results from spectroscopy may be obtained faster than when probes are used. It also has been surmised that vibrational spectroscopy is the most useful type for examination contemplated in the present invention. However, vibrational spectroscopic techniques have not been used for diagnosing disease.
Having resolved that vibrational spectroscopic techniques are useful for diagnosing disease, it becomes necessary to provide a method to practically apply those techniques. In order to apply vibrational spectroscopic techniques, it is principally necessary to understand the spectral characteristics of the cells that are being analyzed.
Normal tissue contains many different types of cells. Each type of cell performs a different function. Abnormal tissue will contain a heterogeneous population of abnormal cells and normal cells. The abnormal cells are derived from the tissue itself or are cells that are not normally found in the tissue. An example of cells that are present in tissue that were not derived for that tissue are inflammatory cells which may accumulate in or around cancerous tissue, or metastases of other cancers.
Cells acquired from a region of tissue may contain several cell types, and thus, such a sample will not be homogeneous. The heterogeneity of this sample may result in spectral information which is not indicative of the information that is potentially available from a single cell because any spectral analysis will involve the average of spectra of different types of cells or the spectra of cells with non-cellular elements in the tissue. Similarly, information about a disease encoded within the molecules of a single cell that is mixed with a heterogeneous population of other isolated cells will also suffer degradation of the information by the averaging of spectra over a range of different types of cells. Therefore, the achievement of the desired accuracy through the use of vibrational spectroscopy will depend on collecting spectra from small elements in tissue that are known to be homogeneous.
It is then possible to map tissue elements by illuminating small areas, or pixels, of tissue sections using an infrared microscope, one pixel at a time. However, this method is time consuming, labor intensive, and requires a skilled operator to move the focus of the microscope to adjacent areas of a sample. Noting these problems, there is a need of a system and method that will permit the collection of spectral data at relatively high speed from many contiguous areas, or pixels, of a tissue sample simultaneously and that will map the distribution of abnormal and normal cells in a tissue sample.